How to make a TreeView?

I tried to use the following: https://github.com/patternfly/patternfly-bootstrap-treeview ...and just spotted that: https://prnt.sc/rymm41 The problem is, that my project is started with Bootstrap 4.

What can I do now ? Is there a way to change the Bootstrapversion of the project afterwards?

Well you certainly don't want to go backwards from BS4 to BS3 just to use a 3rd party sinppet.

Here's a tree using pure CSS which will work in BS4 https://bootsnipp.com/snippets/orp8g

Here are some more options https://www.jqueryscript.net/tags.php?/tree%20view/